Developing websites (mostly using PHP technology and frameworks), working in an "agile" environment. And listening to others, especially when it comes to stuff they're more skilled at!
Ambitious projects which revolve around unexplored concepts that could benefit mostly everyone (as opposed to targetting niche markets).
I've been a web developer since around 2008, after studying computer science and getting a Masters Degree. I've worked on several different personal projects along the way, most of them on the web.
Here are two of them (though not too recent):
http://www.rpgamers.fr/ (french website on RPG video games I used to develop along with a friend)
http://www.teamliquid.net/tlpd (a database of professional Starcraft/Starcraft 2 games)